Determination of Molybdenum, Antimony and Tungsten at sub μg g−1Levels in Geological Materials by ID‐FI‐ICP‐MS

Abstract

We have developed a rapid and accurate method for the determination of Mo, Sb and W in geological samples using isotope dilution inductively coupled plasma‐mass spectrometry with a flow injection system (ID‐FI‐ICP‐MS). The chemical procedure requires HF digestion of the sample with a Mo‐Sb‐W mixed spike, subsequent evaporation and dissolution of Mo, Sb and W from Mg and Ca fluorides with HF. Recovery yields of Mo, Sb and W in the extraction were > 94% for samples of peridotite, basalt and andesite composition, with the exception of W in samples of peridotite composition for which recovery was 81%. No matrix effects were observed in the determination of the isotope ratios of Mo, Sb and W in solutions prepared from peridotite, basalt and andesite samples down to a dilution factor of 100. Detection limits of Mo, Sb and W in silicate materials were at the several ng g−1level. Analysis of the silicate reference materials PCC‐1, DTS‐1, BCR‐1, BHVO‐1, AGV‐1 from the US Geological Survey and JP‐1, JB‐1, ‐2, ‐3, JA‐1, ‐2, and ‐3 from the Geological Survey of Japan as well as the Smithsonian reference Allende powder yielded reliable Mo, Sb and W concentrations. The repeatability in the analysis of basalts and andesites was < 9%. This technique requires only 0.2 ml sample solution, and is therefore suitable for analyzing small and/or precious samples such as meteorites, mantle peridotites and their mineral separates.